Transplant for my Roomba

I just installed my Roomba’s third battery pack. Roomby wasn’t stepped on or anything, like DJ Roomba, but the first pack lost its capacity after a year or so, and a cell replacement didn’t even last that long. I’m hoping that a lithium-ion upgrade is the solution. Unfortunately, the only Li-Ion battery packs offered by iRobot seem to be for their industrial (security, etc.) robots, not for the home models.

Protech Robotics sells a bunch of Roomba supplies, one of which is this lithium battery pack for the Discovery series Roomba. It isn’t cheap, especially compared to the NiMH cell replacement packs that are sold for installation inside the stock battery case. But the amp hours are higher, and these cells should, in theory, hold up through more charge-discharge cycles.

My only concern is the fact that I’m using the stock iRobot fast charger and Roomby himself to charge this new pack. From everything I hear on the automotive side, lithium-cobalt battery packs (which I assume these are, though I’m not entirely sure) need to get past the issues of cell balancing and thermal stability. In this pack, each cell has its own circuit to prevent overcharge, excessive discharge and short circuits — according to the website — which should prevent most thermal issues. But I’m guessing there is no cell balancing happening, since it uses the dumb NiMH charger, so how long can this last? And how do I treat the pack to extend its life as much as possible?

So far, Roomby keeps on kicking for longer cleaning periods than I’ve been able to get from fresh battery packs in the past. The pack looks the same, but it is shockingly lighter than NiMH packs. I hope this helps keep him from getting bogged down on thick rugs during the humid summer months. I’ll post an update after a few months of use.